Re: [HACKERS] Update low-level backup documentation to match actual behavior

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От David Steele
Тема Re: [HACKERS] Update low-level backup documentation to match actual behavior
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Msg-id abf5baad-4207-7a61-e1a8-834d690792c8@pgmasters.net
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Ответ на Re: [HACKERS] Update low-level backup documentation to match actual behavior  (Robert Haas <robertmhaas@gmail.com>)
Ответы Re: [HACKERS] Update low-level backup documentation to match actual behavior  (Robert Haas <robertmhaas@gmail.com>)
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Robert,

Thanks for reviewing!

On 8/18/17 2:45 PM, Robert Haas wrote:
> -     the next WAL segment.  The reason for the switch is to arrange for
> +     the next WAL segment when run on a primary.  On a standby you can call
> +     <function>pg_switch_wal</function> on the primary to perform a manual
> +     switch.
> +     The reason for the switch is to arrange for
> 
> Tacking on "when run on a primary" onto the end of the existing
> sentence is a little ambiguous: does that clause apply only to the
> last part, or to the whole sentence?  I suggest something like: This
> terminates the backup mode.  On a primary, it also performs an
> automatic switch to the next WAL segment.  On a standby, it is not
> possible to automatically switch WAL segments, so you may wish to
> consider running <function>pg_switch_wal</function> on the primary to
> perform a manual switch.

Looks good.

> 
> -    <title>Making an exclusive low level backup</title>
> +    <title>Making an exclusive low level backup on a primary</title>
> 
> I'd omit this hunk.

OK, but I was trying to make it very clear that this backup method only
works on a primary.  If you think the text is in the first paragraph is
enough then I'm willing to go with that, though.

> -     more than one concurrent backup to run, and there can be some issues on
> +     more than one concurrent backup to run, must be run on a
> primary, and there
> +     can be some issues on
> 
> Maybe this would be clearer: This type of backup can only be taken on
> a primary, does not allow more than one ...

Looks good.

> -     This function, when called on a primary, terminates the backup mode and
> +     This function terminates the backup mode and
>       performs an automatic switch to the next WAL segment. The reason for the
>       switch is to arrange for the last WAL segment written during the backup
> -     interval to be ready to archive.  When called on a standby, this function
> -     only terminates backup mode.  A subsequent WAL segment switch will be
> -     needed in order to ensure that all WAL files needed to restore the backup
> -     can be archived; if the primary does not have sufficient write activity
> -     to trigger one, <function>pg_switch_wal</function> should be executed on
> -     the primary.
> +     interval to be ready to archive.
> 
> Why do you want to delete all that text?  It seems like good text to me.

Since the exclusive method only works on a primary...

-- 
-David
david@pgmasters.net



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